#!/usr/bin/env bash
shopt -s nullglob
let playlist_duration_ms=0
for song_file in */*.{mp3,ogg,m4a,flac,wav}; do
  playlist_duration_ms=$(expr $playlist_duration_ms + $(mediainfo --Inform="Audio;%Duration%" "$song_file"))
done
shopt -u nullglob

let playlist_duration_secs=$(expr $playlist_duration_ms / 1000)
let playlist_duration_mins=$(expr $playlist_duration_ms / 60000)
let playlist_duration_remaining_secs=$(expr $playlist_duration_secs - $(expr $playlist_duration_mins \* 60))
let playlist_duration_hours=$(expr $playlist_duration_mins / 60)
let playlist_duration_remaining_mins=$(expr $playlist_duration_mins - $(expr $playlist_duration_hours \* 60))

echo $playlist_duration_hours hours, $playlist_duration_remaining_mins minutes, $playlist_duration_remaining_secs seconds